A port is a communication endpoint of a network connection. A port is identified using a port number for each transport protocol.
A port number is a 16-bit unsigned number ranging from 1 to 65535 which uniquely identifies a port for transport protocol. The port number is always associated with an IP address and a type of transport protocol to be used for communication. Using a port number ensures that arriving packets can be easily forwarded to a running application.
There are two types of port numbers: well-known port numbers and ephemeral port numbers.
Port 80: Used with Hypertext Transfer Protocol (HTTP) to transmit web content from a server to a client over the internet.
Port 21: Used with File Transfer Protocol (FTP) to transfer files between a client computer and server.
Port 433: Used with Hypertext Transfer Protocol Secure (HTTPS) and is an extension of HTTP and runs on SSL.
Port 25: Used with Simple Mail Transfer Protocol (SMTP) to route emails.
Port 53: Used by Domain Name System (DNS) services as an array of communication.
You can use the
-p flag to specify a connecting port. Our managed databases require connecting to port
The port used to connect to the database. DigitalOcean clusters connect on port
25061 by default.
We restrict traffic for TCP and UDP traffic on port 11211 inbound from external networks due to the Memcached amplification attacks in March 2018.
All Droplets for new accounts block SMTP port 25. As an alternative, we recommend using a dedicated email deliverability platform, like SendGrid and generally recommend against running your own mail server.
For custom rules, keep in mind that ICMP has no port abstraction. Also, the default inbound rules allow SSH connections on port 22 from anywhere so that users can manage the server from a terminal.
To learn more about configuring rules, see How to Configure Firewall Rules.